A rare, genetic movement disorder characterized by autosomal dominant, adult-onset, slowly progressive, multifocal, cortical myoclonus. Patients present somatosensory-evoked, brief, jerky, involuntary movements in the face, arms and legs, associated in most of cases with sustained, multiple, sudden falls without loss of consciousness. Seizures or other neurological deficits, aside from mild cerebellar ataxia late in the course of the illness, are absent.